1. Field of the Invention
The present invention relates to a bicycle brake cable control for a cantilevered bicycle brake system in which the positions of the brake pads are adjustable independently of each other.
2. Description of the Prior Art
Most modern bicycles have for some time employed hand operated cantilevered brake systems. In such brake systems the brake controls include hand operated brake actuating levers mounted on the handlebars of a bicycle. Each brake actuating lever is coupled to a central stainless steel multiple strand cable core which may be moved longitudinally in reciprocal fashion within a surrounding cable sleeve. The bicycle hand brake actuating lever is secured to the cable core while one end of the flexible cable sleeve is attached to the hand brake actuating lever mounting. Operation of the bicycle hand brake actuating lever exerts tension on the cable core and draws the cable core longitudinally toward the hand brake actuating lever within the confines of the surrounding cable sleeve.
At the opposite end of the flexible bicycle brake cable a pair of generally U-shaped brake lever arms are typically mounted for rotation about a common axis on the bicycle frame. The brake lever arms are normally secured to the bicycle frame at a fork or a rear seat stay mount on the frame. Frame members extend from the mounting on both sides of a bicycle wheel which rotates within the wheel mounting. The brake lever arms overlap each other and carry brake pads in cantilevered fashion on opposite sides of the bicycle wheel. The flexible, bicycle cable sleeve is secured to one of the brake lever arms for each brake, while the cable core is secured to the other brake lever arm.
The brake lever arms are normally spring biased so that the brake pads are held laterally away from the wheel rim which rotates therebetween. However, when the hand brake actuating lever is operated to pull the brake cable core longitudinally within the cable sleeve, both of the brake lever arms are rotated in mutually opposite directions of rotation about the axis of mounting to the bicycle frame to overcome the spring bias. This moves the brake pads laterally into frictional engagement with the rim of the bicycle wheel located therebetween. The force of friction thereby quickly reduces the speed of rotation of the bicycle wheel within the mounting.
Ideally the brake pads are carried by the bicycle brake lever arms equidistant from the opposite sides of the bicycle wheel rim. Thus, when force is transmitted longitudinally along the flexible bicycle brake cable the brake pads are moved laterally toward the rotating wheel an equal distance and thereupon apply lateral force equally from the opposite sides of the wheel rim. This maximizes braking efficiency. Since the apposing lateral forces are equal and opposite, there is no force component that tends to misalign the bicycle wheel.
Fairly frequently, however, the spacing of the bicycle brake pads from the wheel rim becomes unequal. This may result from many different causes, including bending of the bicycle frame, uneven wear on the engaging faces of the bicycle brake pads, twisting of the lever arms on their axis of rotation relative to the bicycle frame, unequal tension on the bicycle wheel spokes, and other reasons as well.
When the bicycle pads are spaced unequally from the sides of the bicycle wheel, they will apply unequal forces as the bicycle brakes are applied. This detracts markedly from braking efficiency, since the frictional force applied in one lateral direction is greater than that applied in the opposite direction. This increases the minimum distance within which a bicycle can be brought to a stop and also the braking effort which must be applied by the bicycle rider. Furthermore, this condition results in unequal wear on the brake pads and can force the bicycle wheel into a condition of misalignment.
To correct the unequal application of forces by bicycle pads in a cantilevered bicycle brake system, it has heretofore been necessary to concurrently force both of the bicycle brake pads into contact with the bicycle wheel, loosen the nut which secures the brake lever arms to the mounting stud on the bicycle frame, and retighten the nut on the mounting stud to attempt to adjust the positions of the brake lever arms relative to each other so as to equalize the distance from the wheel at which the brake pads reside when the brakes are released.
One problem with the conventional technique for adjusting bicycle brake pads is that the adjustment can be performed only while the brake pads ar concurrently held in contact with the bicycle wheel, as they are during braking. At the same time, however, the bicycle owner must effectuate the necessary loosening and retightening of the brake lever arm mounting system. The concurrent performance of all these tasks is extremely difficult to perform by a user with only two hands, and assistance is often required. Also, it is oftentimes very difficult to secure the brake lever arms in position relative to the wheel so that the brake pads are held at equal distances therefrom when the brake is released. The adjustment of a conventional bicycle brake system is very time consuming and can only be performed with tedious and repeated trial and error adjustment.